EA018125B1 - Cavitating hose mouthpiece - Google Patents

Abstract

The invention relates to fire fighting technology used for fire fighting activity and other emergencies response and can be used for dispersion of extinguishing medium aiming at increase in dispersiveness and consistency created by means of mouthpiece for extinguishing medium spray, which in comparison with a prototype in relation to equal fluid flow makes it possible to achieve higher effectiveness of a mouthpiece due to fine extinguishing medium being obtained. The claimed cavitating hose mouthpiece is characterized in that a cavitating route is designed as successive sections of various configurations: a line narrowing section characterized with a cone angle of 15, a section of spherical contraction, a cylinder section and a conically expanding section characterized with a cone angle of 70°; the length of each section is proportional to the product of according coefficient by the mouthpiece exit diameter which value is defined by the following expression:where π=3.14; ρ - fluid density; Q - fluid flow; ξ - parametric dimension coefficient, equal to 0.98 x 10; v - coefficient of kinematic viscosity of a fluid; p- absolute external pressure outside a mouthpiece.

Description

(57) The invention relates to fire fighting equipment used for fire extinguishing and liquidation of other emergency situations, and can be used to spray fire extinguishing agents in order to increase the dispersion and uniformity of a fire extinguishing jet created by means of a nozzle, which, in comparison with the prototype, at an equal liquid flow rate allows to achieve greater efficiency of the fire barrel during fire extinguishing due to obtaining finely dispersed fire extinguishing composition in the nozzle. The proposed cavitation nozzles are characterized in that the cavitational tract is made in the form of successively arranged sections of various configurations: a linear narrowing section characterized by a taper angle of 15 °, a spherical narrowing section, a cylindrical section and a conically diverging section characterized by a 70 ° taper angle; moreover, the length of each of the sections is proportional to the product of the corresponding coefficient by the diameter of the nozzle outlet, the value of which is determined by the following expression:

where π = 3.14; p is the density of the liquid; ζ) is the fluid flow rate; ξ is a parametric coefficient of dimension equal to 0.98χΙΟ '²; ν is the kinematic viscosity coefficient of the liquid; p _int absolute external pressure behind the nozzle.

The invention relates to fire fighting equipment used for fire fighting and liquidation of other emergency situations, and can be used to spray fire extinguishing agents in order to create a finely dispersed jet.

Known nozzle-spray (patent RB No. 4895, publ. 30.12.2008) on a manual fire barrel, consisting of a cylindrical body, a perforated plate installed in the nozzle body and dividing the total fluid flow into radially symmetric jets, while fine dispersion is carried out by a grid, fixed on the output end of the housing nozzle fixing nut.

The disadvantages of the nozzle are the complexity of manufacturing, low and heterogeneous dispersion of the generated atomized stream of liquid.

Known nozzles of a manual fire barrel according to the patent of the Russian Federation No. 2124913, publ. 01/20/1999, for use at low, medium and high water flow rates in order to reduce its inlet pressure while maintaining the fire extinguishing efficiency in the continuous jet or penetrating long-range dispersed water jet. For this, the output annular channel of the nozzle is made so that the profiles of the output part of the inner wall of the housing and the surface of the output tip of the fairing have a curvature that increases in the direction of exit from the barrel, and the radii of the cross sections of these surfaces decrease in the same direction. With this version of the barrel in the long-range diffused jet mode, the inlet pressure is reduced by an average of 2 times compared with the known barrels. However, the disadvantage of a barrel with a known nozzle is the complexity of its manufacture due to the presence of a combination of an annular channel shape with a scattering body in the form of an ovaloid and, therefore, limited possibilities in the formation of a sprayed jet, in particular when creating a protective screen (water curtain) and torch control at the exit of the nozzle.

Fire trunks are known having an annular outlet channel for water flow. The annular channel is usually formed by the outlet part of the barrel nozzle and the outlet part of the fairing installed in the cavity of the housing, or the wall of the housing and the closed end of the feeding tube installed in the cavity of the housing, for example, U.S. Patent No. 6,518MAT1C-125, US Pat.

Also known fire barrel according to US patent No. 5261494, publ. November 16, 1993. It has an adjustable annular outlet for discharging a continuous stream of water with different jet diameters, which is formed by a cone-shaped outlet tip of a fairing installed in the cavity of the barrel body along its axis and a shaped outlet part of the inner wall of the body. The profiles of the tip and the output part of the inner wall of the body have short sections of mating surfaces that allow the cowl to fit on the wall of the body in order to overlap the barrel. Known fire barrels with an annular outlet channel allow you to change the water flow in a wide range, and also receive, in addition to a penetrating long-range, but relatively narrow torch of small drops of water and water dust, a wide misty torch or umbrella-shaped protective water screen.

The main disadvantage of the known fire barrels with an annular output channel is the relatively random, from the point of view of hydrodynamics, choice of the profile of this channel, which looks from conical to cylindrical or tortuous, but does not provide the possibility of reducing the input pressure of water without loss of fire fighting efficiency. Closest to the proposed is the nozzles according to the patent of RB No. 3950, publ. 10.30.2007, which is made in the form of an annular venturi with a curvilinear confuser, the curvature of which is made hyperbolic. The geometric dimensions of the nozzle are given by an equation relating the hydrodynamic parameters of the jet, its gas content with the radius of the cylindrical part of the nozzle and the cone angle of the diffuser. A fire barrel with this nozzle ensures the supply of a continuous or sprayed (with a varying angle of the torch) jet of water or a solution of a surface-active substance (surfactant), the creation of a water curtain (protective shield) when extinguishing a fire.

The disadvantages of the prototype are low and heterogeneous dispersion of the generated atomized stream of liquid due to the insufficient design of the nozzle of the cavitation effect.

The objective of the invention is to increase the dispersion and uniformity created by means of a nozzle of a jet of fire extinguishing composition, which, compared with the prototype, with an equal flow rate of liquid allows to achieve greater efficiency of the fire barrel during fire fighting due to the receipt of a finely dispersed fire extinguishing composition in the nozzle.

The achievement of the technical goal in accordance with this task is carried out by the fact that a cavitation nozzle of a fire barrel is proposed for producing a finely dispersed fire extinguishing composition, comprising a housing with a connecting thread for a fire barrel, a flow cavitating path, a cylindrical outlet with a set of grids, in which, according to the invention, a flow cavitating path made in the form of four sections of various configurations:

section b _{1 of a} linear narrowing of length B ₁ = (7-8) b ₀ , initial diameter диаметромι = 8ά ₀ and final diameter диаметром2 = (5.8-6.0) άο, taper angle β = 15 °;

plot spherical narrowing length b ₂ = (2,8-3,0) b ₀ ;

cylindrical section b ₃ = 2.5 b ₀ ;

- 1 018125 of a conically diverging section with a length of L ₄ = (1.1-1.2) b ₀ with a taper angle α = 70 °, a diameter of ₄ -1. L and where where ₀ is the diameter of the nozzle outlet; π = 3.1415;

(P ρ is the density of the liquid;

About - fluid flow rate;

ξ is a parametric coefficient of dimension equal to 0.98x10 ^-2 ;

ν is the kinematic viscosity coefficient of the liquid;

r _vn - absolute external pressure behind the nozzle.

The invention is reflected in the drawings, where in FIG. 1 shows a diagram of a cavitating tract; in FIG. 2 - general device nozzle.

The nozzle-sprayer (jet forming device) on a manual fire barrel comprises a housing 5 with a connecting thread 6 for connection to a fire barrel. A flowing cavitating path is enclosed in the casing, providing the formation of a finely dispersed jet of fire-extinguishing liquid and including in series: linear narrowing section 1; plot of spherical narrowing 2; cylindrical section 3; conically divergent section 4. Behind the cavitating path in the nozzle body, its cylindrical outlet part 7 is placed with a set of nets placed in the nozzle if necessary.

The effect of spraying in the fire extinguishing system can be achieved by providing a cavitation mode of fluid flow from the nozzle and spray, which serve as the main cavitating elements. When cavitation occurs in a fluid stream, cavitation microcavities are formed, grow and collapse. Their collapse occurs according to the type of microexplosions, while alternating pulsations of local pressures and velocities and the formation of cumulative microjets occur in the fluid flow. All these factors contribute to improving the quality of spraying, the formation of a finely dispersed spray medium.

The occurrence of cavitation in the nozzles of fire barrels and spray guns, as a rule, can be programmed in the output part. In addition, it must be borne in mind that the development of cavitation is affected by external back pressure at the exit of the nozzle. In this case, this is atmospheric pressure. In the cavities of the inkjet elements (nozzles and sprays) complex hydrodynamic phenomena occur, associated both with the geometry of the inkjet device and with the working medium itself. Accurate accounting of all phenomena associated with the operation of an inkjet device is an almost impossible task. However, based on the research, development experience and the use of hydraulic inkjet devices, the authors developed the following algorithm for calculating the parameters of inkjet devices at a given flow rate and pressure.

When calculating the flow part of the spraying device, it is necessary to take into account the calculated quality of the spraying medium at the given parameters of its outflow, as well as the rheological properties of the sprayed medium and then perform the following steps and conditions:

1) the calculation of the diameter of the outlet - nozzle of the proposed nozzle - is based on ensuring the required flow rate for a given pressure drop. In a first approximation, we set the diameter of the nozzle exit section

where ρ is the density of the liquid;

μ is the flow coefficient (for spray nozzles at the initial design stage, μ = 0.6 [1] can be taken);

About - fluid flow rate;

p is the pressure;

2) calculation of the flow part of the nozzle is based on minimizing hydraulic losses.

A common function performed by nozzles in many inkjet devices is to increase range. In such cases, their geometry represents a smoothly outlined converging channel and the main task of their optimization is determined quite accurately and consists in finding the maximum flow coefficient or the minimum local resistance coefficient.

A fundamentally different situation when calculating nozzles used for spraying liquids. Here, in contrast to the previous case, the appearance of flow instability at the exit from the nozzle is highly desirable, which is usually achieved by sharp fractures of the flow path [2, 3]. The latter measure inevitably causes vortex formation and, ultimately, an increase in losses. Therefore, the goal of optimization in this case is to obtain a solution when, on the one hand, the prescribed instability form must be present, and on the other hand, the nozzle flow coefficient is desirable

- 2 018125 to keep as high as possible. Based on this, a flow path diagram of the spray nozzle was developed (Fig. 1).

The tapering part of the flow path of the nozzle is made in the form of two sections, a section of linear narrowing 1 of length L ₁ and section 2 of a spherical narrowing of length L ₂ . A cylindrical section 3 of length b _{3 is} necessary to create a type of outflow through a hole with a sharp edge. Such outflow conditions provide maximum output disturbance, since the streamlines when approaching the cylindrical section have maximum convergence angles. On the other hand, the length of the cylindrical part of the flow path must exceed its diameter by more than two times. Otherwise, the tear-off region formed at the leading edge (the second source of disturbances) can reach the outlet and smooth out the effect of outflow through the hole with a sharp edge.

For the expanding part 4 of length b ₄ , an opening angle such that the outflow occurs so that the liquid does not touch the walls should be adopted. This is ensured at an angle α = 70 °.

Experiments with high-speed jets [3] showed: a minimum of hydraulic losses is observed at taper angles β = 13-15 ° and a ratio of diameters at the inlet and outlet of the nozzles Ό ₁ / ά ₀ > 8, therefore, in the calculations we take (2)

D = 8 <ή,

It is recommended that the length of the linear narrowing of b ₁ be assigned no more than B ₁ [5], therefore we take the length of the linear narrowing equal to B ₁ , i.e.

£, = 8 (ή)

Define the final diameter of the linear contraction E ₂

D = 0, -21d β] 2 D = 8s / ₀ - 16 (d (^ / 2)

We take the angle β = 15 °, we get ⁼ 6.0 {/ o

Find the length of the spherical narrowing (3) (5) (4)

1-2 = 2

(θ) or

1.2 = Z.Os / o (7)

The flow path is designed so that the surface outlined by the nozzle of the conoidal profile, ensuring a minimum of hydraulic losses, fits into its internal cavity. Such a profile of a tapering nozzle can be calculated by the Vitoshinsky formula [4] where r, x are the current transverse and longitudinal coordinates

R0 = 0.501 (9) r = O, 5c1 _o (10)

1 * 1 + 1 ^ 2 + Tu

7z (11)

Assuming that the inlet and outlet edges of the flow path of the nozzle lie on the Vitoshinsky profile, we determine the length of the cylindrical section. In this case, the radial coordinate of the desired point is known. Since the desired value of x is implicitly specified, we determine it by choosing r ₁ , then the length of the cylindrical section 3 is determined as

The length of the expanding part of the flow path at α = 70 ° will be = 1.1 </ o (13)

3) Calculation of the nozzle using the effect of cavitation.

The occurrence of cavitation in the considered type of channel can occur in the cylindrical section 3. In addition, it should be borne in mind that the emergence and development of cavitation is affected by the external back pressure at the exit of the nozzle. In this case, this is atmospheric pressure.

Cavitation phenomena in the nozzle nozzle occur under the condition [1]

Ren> Rnp ⁺ , where p _int - pressure behind the nozzle;

r _np - saturated vapor pressure;

ρ is the fluid density;

θ is the average velocity at the exit of the nozzle;

(14)

- 3 018125 β - nozzle taper angle.

After the transformations, neglecting the saturated vapor pressure due to its smallness compared to the pressure in front of the nozzle, we obtain a formula for determining the diameter of the outlet required to achieve the cavitation effect when the fire extinguishing fluid passes through sections 1-3 of the cavitating nozzle:

where π = 3.1415;

ρ is the fluid density;

About - fluid flow rate;

ξ is a parametric coefficient of dimension equal to 0.98x10 ^-2 ;

ν is the kinematic viscosity coefficient of the liquid;

R _int - absolute external pressure behind the nozzle.

The nozzle works as follows.

Water or a solution of a surfactant through a hand-held fire barrel with a housing 5 screwed onto it through a connecting thread 6, the nozzle enters the linear narrowing section 1 of the cavitating path, where the total flow focuses on the spherical narrowing section 2 along the decreasing diameter of the cone. the liquid stream of the necessary kinetic energy, section 1 has the following parameters (Fig. 1): length B | = (7-8) b ₀ . initial diameter Όι = 8ά ₀ ; final diameter Ό ₂ = (5.8-6.0) ά ₀ ; where ά ₀ is the diameter of the cylindrical section 3; taper angle β = 15 °.

In order to reduce the inlet pressure of the extinguishing fluid, the diameters of the cross sections of the inner wall of the section 1 of the cavitation path are reduced in the direction of exit from the nozzle, and the inner surface of the section 2 of a spherical narrowing along its length equal to L ₂ = (2.8-3.0) b ₀ , made with curvature increasing towards the exit from the trunk. With this embodiment, the input part (linear and spherical narrowing sections 1, 2) of the cavitating path, the nozzle fluid, under the action of a centripetal force from the side of the inner wall with increasing curvature of section 2, in any axial longitudinal section of the channel acquires a rotational movement towards the entrance to the cylindrical section 3, forming a swirl. The length of the cylindrical section b ₃ = 2.5 b ₀ . Since ά ₀ <Όι, the cylindrical section 3 is not able to pass all the fluid as fast as it enters the nozzle inlet, therefore, an increase in the current local velocities of the vortex flows of the fluid creates changes in its uniform pressure. Thus, at the entrance to section 3, the pressure of the extinguishing liquid decreases due to an increase in local velocities in its flow due to a collision with a curving surface, and a hydrodynamic cavitation effect occurs, which leads to saturation of the liquid with gas (vapor) bubbles and an increase in its fineness. The conically divergent section 4 serves to form the torch of the extinguishing jet at its outlet from the nozzle. The optimum parameters of section 4 were experimentally confirmed: length b ₄ = (1.1-1.2) b ₀ with the corresponding taper angle α = 70 °.

The final fine spraying of water jets occurs on a set of grids in a cylindrical output part 7 installed at the outlet of the nozzle of the sprayer.

Claims (5)

CLAIM 1. Cavitational fire nozzle trunk, comprising a housing with a connecting thread for a fire shaft, a flow-through cavitating path, a cylindrical outlet with a set of grids, characterized in that the flow-through cavitating path is made in the form of successive sections of various configurations: 15 °, a spherical constriction section, a cylindrical section and a conically diverging section, characterized by a taper angle of 70 °, with the length of each and The plots are proportional to the product of the corresponding coefficient for the diameter of the nozzle outlet, the value of which is determined by the following expression: - 4,018,125 256ρ ^ β ^ р _ш 4з7 where π = 3.14; ρ is the density of the liquid; Ρ - fluid flow rate; ξ is a parametric dimensionality factor equal to 0.98x10 ^-2 ; ν — coefficient of kinematic viscosity of a liquid; p _vn - absolute external pressure behind the nozzle. 2. Nozzles according to claim 1, characterized in that the linear constriction section has the following parameters: a length of 7 to 8 times the diameter ά ₀ of the nozzle outlet, the initial diameter is 8 ά ₀ , and the final diameter is 5.8 to 6 times greater than ά ₀ . 3. Nozzles according to claim 1, characterized in that the length of the spherical constriction section is from 2.8 to 3 times the diameter ά ₀ of the nozzle outlet. 4. Nozzles according to claim 1, characterized in that the length of the cylindrical section 2.5 times its diameter ά ₀ . 5. Nozzles according to claim 1, characterized in that the length of the conically diverging section is 1.1 to 1.2 times the diameter ά ₀ of the nozzle outlet.